<?php

/*
 * This file is part of SwiftMailer. (c) 2004-2009 Chris Corbyn For the full copyright and license information, please view the LICENSE file that was distributed with this source code.
 */

/**
 * Provides fixed-width byte sizes for reading fixed-width character sets.
 * 
 * @package Swift
 * @subpackage Encoder
 * @author Chris Corbyn
 * @author Xavier De Cock <xdecock@gmail.com>
 */
class Swift_CharacterReader_GenericFixedWidthReader implements Swift_CharacterReader {
	/**
	 * The number of bytes in a single character.
	 * 
	 * @var int
	 * @access private
	 */
	private $_width;
	
	/**
	 * Creates a new GenericFixedWidthReader using $width bytes per character.
	 * 
	 * @param int $width        	
	 */
	public function __construct($width) {
		$this->_width = $width;
	}
	
	/**
	 * Returns the complete charactermap
	 *
	 * @param string $string        	
	 * @param int $startOffset        	
	 * @param array $currentMap        	
	 * @param mixed $ignoredChars        	
	 * @return $int
	 */
	public function getCharPositions($string, $startOffset, &$currentMap, &$ignoredChars) {
		$strlen = strlen ( $string );
		// % and / are CPU intensive, so, maybe find a better way
		$ignored = $strlen % $this->_width;
		$ignoredChars = substr ( $string, - $ignored );
		$currentMap = $this->_width;
		
		return ($strlen - $ignored) / $this->_width;
	}
	
	/**
	 * Returns mapType
	 * 
	 * @return int mapType
	 */
	public function getMapType() {
		return self::MAP_TYPE_FIXED_LEN;
	}
	
	/**
	 * Returns an integer which specifies how many more bytes to read.
	 * A positive integer indicates the number of more bytes to fetch before invoking
	 * this method again.
	 * A value of zero means this is already a valid character.
	 * A value of -1 means this cannot possibly be a valid character.
	 * 
	 * @param string $bytes        	
	 * @return int
	 */
	public function validateByteSequence($bytes, $size) {
		$needed = $this->_width - $size;
		
		return ($needed > - 1) ? $needed : - 1;
	}
	
	/**
	 * Returns the number of bytes which should be read to start each character.
	 * 
	 * @return int
	 */
	public function getInitialByteSize() {
		return $this->_width;
	}
}
